676 Scientific Proceedings, Royal Dublin Society. 



a potato-maslier. About 80 c.c. of juice were thus obtained, to which was 

 added an equivalent quantitity of water. This was allowed to stand over 

 night in a tall cylinder, when the starch-grains and other suspended solid 

 matter became sedimented. The supernatant liquid was siphoned off and 

 filtered through a Chamberland filter into a sterile flask, the sterile juice 

 being then distributed into sterile flasks. A portion of the unfiltered (non- 

 sterile) juice was also transferred to a sterile flask. Ten flasks were inoculated 

 from a pure culture of P. infestans, and were allowed to stand at room- 

 temperature for a considerable period, while side by side with them stood 

 similar uniuoculated flasks containing the juice as controls. During this 

 time, somewhat to our surprise, the fungus made little or no apparent 

 growth in any of the flasks. 



The experiment was repeated at a later date, flasks containing the filtered 

 (sterile). and unfiltered juice being inoculated with both conidia and small 

 portions of mycelium from a pure culture. No growth whatever occurred in 

 the unfiltered juice, possibly because it rapidly underwent putrefactive 

 decomposition at the hands of bacteria. The filtered juice remained sterile, 

 but where inoculated with conidia no growtli occurred. When mycelium 

 from a pure culture, however, was placed in the filtered juice, it not only 

 remained alive for about three weeks, but increased in amount to a small 

 extent. This freshly developed mycelium frequently presented curious 

 deformities in structure some of which are illustrated iu figs. 1, 2, and 3, 

 Plate XLYI. We do not consider these structures as being attempts at the 

 formation of sexual organs ; but in many instances they certainly would 

 seem to be malformed or abortive conidia,' their condition being due in all 

 probability to the fact of their being submerged in a liquid, and not produced, 

 as is normally the case with P. infestans, in the air. Our experience as well 

 as that of other workers, such as Himmelbaur, seems to show that the produc- 

 tion of hyphae, with abnormal growth, is more or less common in several 

 species of Phytophthora when cultivated on artificial substrata. 



(3) Growth in Potato-juice Agar and Potato-juice Gelatine. — The potato-juice 

 is prepared in the cold as above, and then boiled and filtered. It is stiffened 

 by the addition of 10 per cent, to 12 per cent, of gelatine or 1'25 per cent. 

 of agar. The juice is naturally slightly acid, and the addition of gelatine 

 renders the medium still more acid. In some cases the acidity of the gelatine 

 was neutralized before use — in others not. 



On these media growth certainly takes place, and conidia are to some 



' Some of the stiuctures figiu'ed by Jones as occurring iu potato-gelatine cultures would also 

 seem to be susceptible of a similar interpretation. 



